Receiver for diversity reception



Aug. 6,- 1940. A. VfLouGHREN l 42,210,08`9v- 4 RECEIVER FOR VDIvERsITY REcEffTIoN n Filed Dem 16, 19:58

INVENTOR Hun v. LousHREN ATTORNEY Patented Aug. i

PATENT oFFicE RECEIVER. Fon nIvEns'rrY vRECEPTION -I Arthur V. Loughren, Tuckahoe, N. Y., assignor to Hazeltine Corporation, a corporation of Delaware Application December 1 s claims.

This invention relatesto a receiver for diversity reception and particularly to such 'a re'- ceiver comprising means to provide preset tuning for particular stations.

s Transmitted modulated-carrier'signals are subject to fading which varies in an unpredictable manner both in frequency and degree. The fading at any instant may differ very widely geographically or in different planes of polarization. It has been suggested to provide a modulatedcarrier wave-signal receiver with a number of physically spaced 'or electrically diverse antennas having, consequently, different fading charac- Iteristics, the'signals received by the several an- 15 tennas being reproduced by a single reproducing means. Transmitted modulated-carrier energy fluctuates not only in intensity, but in phase, so that there may be considerable relative phase fluctuation at the several antennas ofsuch a sys- For this reason, it is impracticable directly to combine the received radio-frequency energies. In some instances, it has been found to be practicable to combine the detected energies of such received signals. However, if there is a phase difference between the carrier frequencies of the signals at the dierent antennas,` phase fluctuations in the beat notes-oi' the carrier and the sideband frequencies are pro. duced which may preclude satisfactory operation of a -receiver of the last-mentioned type. In order to eliminate posed to reproduce only the signal which is received with maximum amplitude by means of' an arrangement which instantaneously effectively shifts the reproduction to the channel receiving the strongest signal. Means comprising relays for accomplishing this purpose cause a temporary variationin the volume of the reproduced signal when the transfer between chano nels is made and'for this reason it has been proposed to utilize an automatic volume control of each receiving channel is also effective upon each of the other receiving channels of the system. With such an arrangement, it is possible tov tune the several channels of the receiver to different stations 20 tem.

carrying'the same program rand procure a rel ception which i's generally satisfactory. Such a y system, however, requires tuning of several channels ln addition-to those of4 conventional modulated-carrier signal receivers. For this reason, the operation of the receiver is very difficult for anyone other than a skilled operator. It isfirst necessary to determine independently the yvar- 55 ious stations4 which are carryin the same prothis diiliculty, it has been protubes or arrangement in which the 6, 1938, Serial No. 246,018 l gram and then separately to tune each of the receiving channelsto one of theser stations and thereafter provide for'combining the output of the three channels'in a single reproducing means.

Itis an object of this invention to provide a modulated-carrier wave-signal Areceiver of the character described in which the above-mentioned diiculties are eliminated.

It is still another object of the invention to provide a diversity receiver comprising ai' Preset tuning arrangement for simultaneously tuning' a plurality of channels of the receiver 'to various predetermined stations carrying a common program.

In accordance with the present invention, there is provided in a diversity broadcasting system including a plurality,v of carrier-wave signaltransmitting stations'jwhich are geographically spaced, which transmit on different carrier-frequencies, and which carry a' common program, 0 a diversity receiver comprising a plurality of signal-translating channels. Apreset tuning arrangement is included in each of the channelsv adapted to tune each ofthe vchannels to a different predetermined one of the stations of the system. Thereis also provided unicontrol means for the tuning arrangements adapted to tune each of the channels to its respective predetermined station carrying the common program.

In accordance .with a preferred embodiment of the invention, there is provided means for causing reproduction of signals in the channel receiving signals of greatest amplitude and for suppressing reproduction in the other receiving channels. In the preferred embodiment of the invention, :preset tuning condensers are provided for each yof the channels adapted to be switched by the unicontrol means-to condition the receiver for diversity reception; one position of the unl- `control means providing vfor the use'of one of the receiver channels as a conventional modulated-carrier signal receiver manually tunable to any frequency within a predetermined band of frequencies, such'as theA normal broadcast band. i

Theqnovel features which are believed to be characteristic of this invention are set forth with particularity in the appended claims. "The invention itself, however, both as to-its organization and'method of operation, together withf'urther objects and' advantages thereof, will best be understood with reference to the following specification taken in connection with they accompanying drawing,`the single gure of whichis a circuit n diagram of a complete superheterodyne receiver utilizing the present invention.

Referring now more particularly to the drawing, there is shown a circuit diagram, Apartly schematic,of a diversity receiver of the superheterodyne type including unicontrol meansv for conditioning the several channels of the receiver for diversity operation. Brieiiy described, the receiver includes three separate receiving channels, each of which contains the conventional elements of a modulated-carrier signal receiver of the superheterodyne type. Similar circuit elements in the three signal channels have been given identical reference numerals, subscripts a, b, and c being utilized to identify a particular element with a particular receiving channel. Thus, one oi the channels, speciiically channel a, comprises a radio-frequency amplifier lila having input terminals connected to an antenna Ha and ground I 2a and output terminals coupled to a frequency changer or modulator |3a including an oscillator I 4a which may be separate, as or a unitary Vpart ofthe modulator l3a. Connected in cascade with the output circuit of the frequency` changer unit 13a, in the' order named, are an intermediate-frequency amplifier 55a, Va detector and automatic ampliilcation control unit Ilia, an audio-frequency ampliiier lla,

and a sound reprbducer I8 which is common to the three signal-translating channels of the receiver.

frequency amplier i5a and detected by tietector lBa, thereby producing the audio irequencies of modulation which are, in turn, amplied by audio-frequency amplier Ila and reproduced by the sound reproducer I8.

Referring now more particularly to the details of the system comprising the present invention, there is provided a preset tuning arrangement for each receiving channel of the receiver. Only the essential elements of the selector circuits o1' the radio-frequency ampliner, the modulator, and the oscillator of each of the receiving channels are illustrated in the drawing. Thus, the selective circuit of radio-frequency amplifier Illa includes an inductance 20a, adapted te be tuned by a selected one oi condensers 21a, 22m-and 23a whichmay be switched into the receiver circuit by means of switch 24a. 'Ihe corresponding elements of modulator Ila and oscillator Ila are similar and have been given identical reference Y numerals. Channel c differs slightly from that of the other two channels in that, in the fourth position of switches 24e, variable tuning condensers ying the tuning inductances automatically controls its own operating all of the selector'switches'rla, 2lb,

and 24e. A separate unicontrol mechanism `2S" is provided for the variable condenser 26 of channel c. In order that only that receiver channel receiving signals of greatest amplitude4 may be controlbias of each channel is eiective upon one or more stages of its respective channel and is also effective upon one or more stages of each of the other channels.

In considering the operation o f the system just described, it will be assumed that the several corresponding sets of condensers Zla, 2lb, 2Ic; 22a, 22h, 22e; and 23a, 23h, 23o are initially preset to such adjustments as to tune the three channels to diiierent stations which generally transmit the same program, that is, to different stations of a network of stations which are geographically spaced, which transmit on diierent carrier frequencies, and which carry a common `program. Under such conditions, by operation of operative due to the fact that inductors 20a and 20h of the selector 'circuits are short-circuited by the switches 24a, 24h. By virtue of the cross connection of the automatic volume control circuits, that channel which at any given time is translating the signal with greatest amplitude not only ampliiication in a normal manner, but also supplies to each of the other channels anl ampliiication control. bias which is abnormally large for the lower amplitude signals translated by such other channels so that their-signal output is considerably less than that of the rst channel. For even a very slight initial difference in the signal strengths at the antennas, the strongest .signal is amplified normally but simultaneously weakens a weaker signal which, in turn, relaxes the amplification control of the stronger signal so that simultaneously the weaker signal is'almost completely cut out and reception depends almost entirely upon the stronger signal. Thereafter, the arrangements will notA reproduce energy received from an antenna which has been cut out even if its signal should grow stronger, except in the case where the signalv which is being reproduced fades below a predetermined level, in which event the amplification control is shifted rapidly so as to amplify and reproduce the signal which is then avmaximum. Thus there is selected for effective operation, from among the several antennas, that antenna at which the received signal is the strongest and the signal received thereby is amplied by its associated channel practically exclusively of, or at least predominantly over, those translated by the other channels. For this reason, there is littleeconict of reception due to the different phase fluctuations of the diiierent antennas, and automatic volume control i'or the eil'ective receiver channel is thus provided in a conventional manner.

While there have been" llustrated. rotary switches'for conditioning the receiver for. diversity operation. it will be understood that pushf button or. other equivalent tuning can be utilized.

for said It will also be understood that, in case diilicuity is experienced in finding three stations carrying any one of the receiver channels, when conditionedfor diversity operathe desired program,

.those skilled in the art thatv various changes and modiiications may be made therein without departing from the invention, and it is, therefore, aimed in the appendedclaims to cover all su'ch changes and modiilcatlons as fall within the true A spirit and scope of the invention.

What is claimed is: 1. In a diversity broadcasting system including a plurality of modulated carrierwave signaltransmitting stations which are geographically spaced, which transmit on different carrier irequencies, and which carry a common program, a diversity receiver comprising, a plurality of signal-translating channels, a preset tuning arrangement for each of said channels adapted to tune each of said channels to a different predetermined one of said stations, and unicontrol lmeans for said tuning arrangements adapted to tune each oi said channels to its respective predetermined station carrying the common'program.

2. In a diversity broadcasting system including a plurality of modulated carrier-wave signaltransmitting stations which are geographically spaced, which transmit on diiIerent carrier frep 40 quencies, and which carry a common program, a

diversity receiver comprising, a plurality of signal-translating channels, a rangement for each of said channels adapted to provide selective tuning of each of said channels to any oi a plurality o! said stations.'and unlcontrol means for said tuning arrangements adapted simultaneously to tune each of said channels to a different said stations carrying the common program.

A 3. In a diversity broadcasting system including a plurality of modulated carrier-wave signaltransmitting stations which are geographically spaced, which transmit on'diiferent carrier trequencies, and which carry a common program,.a

diversity receiver comprising, a plurality; ol.' signal-translating channels, a rangement for each of said channels adapted t0 provide selective tuning o! said channels to-any of a plurality of said stations, unicontrol means tuning arrangements adapted simultaneously to tune each of said channels' t0 a diilerent predetermined one of lsaid stations carrying the' common program, and means fon signals by the channel receiving signals of greatest amplitudeanci for 'v causing translation of A substantially suppressing translation by the others of said channels. v

4. In a diversity broadcasting system including ya plurality or modulated carrier-wave signal- 7o transmitting stations which are geographically fspaced, which transmit on diilerent carrier fre- VYquencies, and which carry a common program, a

diversity'l receiver comprising, a plurality of signal-translating channels, a preset tuning arrangement for each of said channels adapted to transmitting stations which preset tuning arpredetermined one or preset tuning arprovide selective tuning of each o! said;

to any of a plurality of said stations. unicontrol means for said tuning arrangements adapted .simultaneously to tune each of said channels to a different predetermined one or saidstations .5 carrying the common program, and means responsive to the amplitudes oi signals received by said channels for causing translation of signals by the channel receiving signals oi greatest amplitude and for substantially suppressing trans- .-10 lation by the others of said channels. f 5. In a diversity broadcasting system including a plurality of modulated carrier-wave signalare. geographically spaced,'which transmit on diilerent carrier fre- 15 quencies, and which carry a common program, a diversity. receiver comprising, a plurality of signal-translating channels, a preset tuning arrangement !or each o! said channelsl adapted to provide selectivetuning of each of said channels to any cfa plurality of said stations, unicontrol means for said tuning arrangements adapted simultaneously to tune each of said channelsto a diilerent' predetermined one oi' said -stations carrying the common program, and means for 25 controlling the amplication in each of said channels partially inversely in accordance with the amplitude of the signal received by the channel and partially inversely in accordance with the amplitudesof tliezsignals received by 30 the other chann i 6. In a diversity broadcasting system including a plurality of modulated 'carrier-wave signaltransmitting stations which are geographically spaced, which transmit on vdiierent carrier fre- 35 quencles, and which carry a common program, a diversity receiver comprising, a plurality loi sig nal-translating channels, a preset tuning arrangement for each oi!l said channels adapted tov provide selective tunin of each o! said channels 40 to any of a plurality f said stations. a variable tuning means for one of said channels for continuously tuning said one of vsaid channels to any frequency within a predetermined band of ,frequencies and means comprising unicontrol 45 means for selectively tuning each of said channels simultaneously to a'dierent predetermined one of said stations carrying the common program orior inserting said variable tuning means in said one of said channels to condition said 5 one o! said channels to be tuned to any of said frequencies within said band.

7. In a diversity broadcasting ,system including a plurality of modulated carrier-wave signaltransmitting'stations which are geographically 55 spaced, which transmit on diilerent carrier rre'- quencies, and which carry a .common program, a diversity receiver comprising. a plurality of signai-translating channels, a preset tuning arrangement comprising a plurality or adiustably w fixed-tuned elements for each of said channels .adapted to provide selective tuning of each oi said channels to any of a plurality of said stations, and switching means for selectively including predetermined ones of said fixed-tuned g5 v elements simultaneously in their e respective channels to tune each voi-said channels to the diilerent predetermined 'one oi.' saidstations cara common program. 8. vIn a diversity broadcasting system including 70 a plurality of modulated carrier-wave signaltransmitting stations which, are geographically spaced, which transmit on different .carrier irequencieaand which carrya ,connnon program, adiversity receiver comprising, a Vplurality o! s ig nal-translating channels, a. preset tuning arrangement comprising a plurality of adjustably fixed-tuned condensers for each of said channels` adapted to provide selective tuning of each of said channels to any of a plurality of said stations, and switching means for selectively inmon program.

cluding predetermined ones of said condensers simultaneously in their respective channels to 'tune each of said channels to a diierent prede- 

